The intercostal muscles comprise many different groups of

muscle Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...

s that run between the ribs, and help form and move the

chest wall The thoracic wall or chest wall is the boundary of the thoracic cavity. Structure The bony skeletal part of the thoracic wall is the rib cage, and the rest is made up of muscle, skin, and fasciae. The chest wall has 10 layers, namely (from ...

. The intercostal muscles are mainly involved in the mechanical aspect of

breathing Breathing (spiration or ventilation) is the rhythmical process of moving air into ( inhalation) and out of ( exhalation) the lungs to facilitate gas exchange with the internal environment, mostly to flush out carbon dioxide and bring in oxy ...

by helping expand and shrink the size of the chest cavity.

Structure

There are three principal layers: # External intercostal muscles also known as intercostalis externus aid in quiet and forced

inhalation Inhalation (or inspiration) happens when air or other gases enter the lungs. Inhalation of air Inhalation of air, as part of the cycle of breathing, is a vital process for all human life. The process is autonomic (though there are exceptions ...

. They originate on ribs 1–11 and have their insertion on ribs 2–12. The external intercostals are responsible for the elevation of the ribs and bending them more open, thus expanding the transverse dimensions of the

thoracic cavity The thoracic cavity (or chest cavity) is the chamber of the body of vertebrates that is protected by the thoracic wall (rib cage and associated skin, muscle, and fascia). The central compartment of the thoracic cavity is the mediastinum. Ther ...

. The muscle fibers are directed downwards, forwards and medially in the anterior part. # Internal intercostal muscles also known as intercostalis internus aid in forced

expiration Expiration or expiration date may refer to: Expiration Expiration may refer to: *Death *Exhalation of breath, breathing out * Expiration (options), the legal termination of an option to take an action *Shelf life, or the time after which a product ...

(quiet expiration is a passive process). They originate on ribs 2–12 and have their insertions on ribs 1–11.Their fibers pass anterior and superior from the upper margin of the rib and costal cartilage to the lower margin of the rib above.(source)
The internal intercostals are responsible for the depression of the ribs and bending them inward, thus decreasing the transverse dimensions of the thoracic cavity. The muscle fibers are directed downwards, forwards and laterally forming right angle with external intercostal muscle. # Innermost intercostal muscle also known as intercostalis intimus are deep layers of the internal intercostal muscles which are separated from them by a neurovascular bundle. The muscle fibers are directed downwards, forwards and laterally same as intercostalis internus muscle.

Nerve supply

Both the external and internal muscles are innervated by the intercostal nerves(the ventral rami of thoracic spinal nerves), are supplied by the

intercostal arteries The intercostal arteries are a group of arteries passing within an intercostal space (the space between two adjacent ribs). There are 9 anterior and 11 posterior intercostal arteries on each side of the body. The anterior intercostal arteries a ...

, and are drained by the intercostal veins. Their fibers run in opposite directions.

Function

The scalene muscles, which also move the chest wall and have a function in inhalation, are also intercostal muscles, just not one of the three principal layers.

References

External links

*
UCC
* Gray's Anatomy 41st Edition {{Muscles of thorax and back Muscles of the torso

Structure

Nerve supply

Function

See also

References

External links